1. Field of the Invention
This invention relates to adaptive processor systems, and more particularly, to a novel phase weighted adaptive processor system for use in radar altimeters, transmitter-receiver systems, null and/or steeering systems such as used in phased array antennas and sidelobe cancellation systems.
2. Description of the Prior Art
Prior art adaptive processor systems are known and have been described in text books. Adaptive processors have been employed in sidelobe cancellation systems and for countering anti-radar jamming devices. Such prior art systems have employed parallel signal paths and a pair of amplitude modulators which are phase shifted ninety degrees, one from the other. Such systems are described in U.S. Pat. No. 3,881,177 which describes a system for cancelling an undesired signal.
When the undesired signal is much stronger than the desired signal, it often masks the desired signal to the extent that the desired signal cannot be properly recovered.
Prior art adaptive processors employed numerous elements which are and were susceptible to signal dispersion. Quadrature power splitters, as employed in the prior art are designed for changing the phase of a signal exactly ninety degrees. These devices are not highly accurate, and if several such quadrature power splitters are employed in a single adaptive processor system, the added effect of the error in such devices can produce inaccurate cancellation signals.
It is difficult to obtain a ninety degrees phase shift with phase shifters. Further, in high frequency adaptive processor systems, there are line delays and component delays which can cause phase shifts. Temperature and the age of components and the frequency of the signal applied to components may change the phase shift and/or delay encountered by the signals in a system. Even if the components are properly tuned when a system is manufactured, they are susceptible to drift and changee in use.
Prior art adaptive processors are complex and require expensive components for accurate results. The mode of operation of the aforementioned prior art adaptive processors employ amplitude modulation for the adjustment of the phase of the signals to cancel unwanted weak signals. These prior art systems are expensive and difficult to keep in tune.
It would be extremely desirable to provide an adaptive processor system which is more accurate than prior art adaptive processing systems and is cheaper to build and would eliminate undesired signals.